I lost the source of Zeta Vintage, and an attempt to do an rewrite in C showed again that the 6502 processor should really be programmed in assembly, so a rewrite in 6502 assembly is still on my bucket list...

Zeta and Zeta Dva support only some basic Xboard protocol commands and some users have reported problems with the configuration and interface of the last Zeta versions.‭ ‬So i will publish the source code again when these parts are more user friendly designed and tested for Windows Chess-GUIs like Winboard or Arena.